Principles of Diagnosis

A diagnosis requires a high index of suspicion, especially in areas where the disease is not prevalent. Bone and joint tuberculosis is usually an indolent, slowly progressive disease, with patients often presenting with nonspecific constitutional symptoms such as low-grade fevers, night sweats, weight loss, anorexia, anemia, and malaise. Lymphadenopathy is common. Extremity involvement may present with localized pain and increased warmth, soft tissue swelling or effusion, loss of motion, and limp or gait disturbance. The initial evaluation includes a chest radiograph, complete blood count, and ESR. Normal acute phase reactants do not rule out the presence of tuberculosis. The purified protein derivative (PPD) tuberculin skin test is often positive in endemic areas or in patients who have received the BCG vaccination and does not correlate with active disease.

The microbiologic diagnosis of tuberculosis in austere settings depends on the evaluation of sputum smears, and smears and cultures of biopsy specimens, using Ziehl-Neelsen and Auramine O stains. Acid fast bacilli and granulomas seen on direct microscopy lead to the fastest diagnosis but are present in less than 50% of cases. A formal biopsy may be difficult to obtain especially in those with spinal involvement. Cultures are positive in up to 90% but often take 6–8 weeks to become positive.

Treatment Principles

Chemotherapy remains the mainstay of treatment for all forms of tuberculosis and is generally effective in 90% of cases. Surgery is indicated for (1) establishing the diagnosis and (2) treating complications of the disease. Ideally a biopsy and culture should guide therapy, but this is impractical in low-resource environments. Empiric chemotherapy is provided in many cases when the characteristic clinical and radiographic features are present. In previously untreated adults without known drug susceptibility, rifampin and isoniazid should be used throughout the duration of therapy, and another first-line drug, streptomycin or ethambutol, is chosen for the first 2 months along with one second-line drug.

Most patients with active TB are treated with 6–9 months of therapy [1, 2], though some practitioners favor treating spinal disease for 12–18 months. The WHO treatment guidelines should be followed [2], and systems for monitoring compliance, such as DOTS – directly observed therapy, short course – should be in place. A longer duration of chemotherapy may be indicated with documented cases of relapse and in patients who exhibit signs of persistent inflammation, known as slow responders. Specific recommendations are available for patients with recurrent disease and active disease associated with HIV/AIDS. In contrast to abscesses associated with bacterial sepsis, cold abscesses may resolve with chemotherapy, and drainage is not routinely required. Bacterial superinfection should be suspected when a sinus track fails to close following an adequate course of chemotherapy.

Lack of adherence to treatment with chemotherapy commonly leads to the development of resistant strains that are more difficult and costly to treat. DOTS regimens have been developed to counter this but require intense resources, which are often lacking. Screening for drug toxicity is limited, and patient education about side effects and potential complications of treatment is crucial.

Multidrug-resistant TB is defined as resistance to isoniazid and rifampicin, while extensively drug-resistant tuberculosis describes resistance to isoniazid, rifampicin, and several second-line drugs [3]. Most of these resistant cases reflect the failure of the system to provide the correct medications and dosages and to monitor treatment. The incidences of these worrisome entities are on the rise.

Osteomyelitis

Osteomyelitis is the least common form of musculoskeletal TB (5%), and the presentation is similar to subacute hematogenous osteomyelitis. Clinically, patients present with pain and soft tissue swelling, and both abscesses and sinuses are common. Most patients are adequately imaged with plain radiographs.

The differential diagnosis on plain radiographs is extensive and includes chronic osteomyelitis, Brodie’s abscess, benign and malignant tumors, and other granulomatous diseases. While a lytic lesion with or without a sclerotic rim is the most common presentation, lesions may be serpiginous, commonly cross the physis, and may readily invade neighboring joints (Fig. 33.2a–d). An aggressive periosteal response can also be observed, and in such cases a biopsy is mandatory.

Sequestrae are unusual but can be present. The entire diaphysis can become sequestered in children due to intraosseous thrombosis. Disseminated skeletal tuberculosis can be observed in compromised hosts, involving combinations of osseous and articular involvement. Tuberculous dactylitis, spina ventosa, occurs in the short tubular bones of the hands and feet. X-rays show multiple layers of subperiosteal new bone, a finding diagnostic for tuberculosis (Fig. 33.2d).

Given this diversity in plain radiographs, a biopsy is helpful in establishing the diagnosis, recognizing that under selected circumstances empiric treatment is considered. While curettage is recommended at the time of biopsy, bone grafting is rarely required as the lesions heal with chemotherapy. In severe and recalcitrant lesions, antibiotic-loaded bone cement (polymethyl methacrylate PMMA) spacers may be considered as well. While rifampin has been shown to be unsuitable for delivery through bone cement, isoniazid and streptomycin have shown beneficial elution parameters [4].

Arthritis

The natural history of TB arthritis progresses over several years, beginning with synovial seeding or direct penetration from a metaphyseal focus and culminating with joint destruction. The host inflammatory response results in synovial hypertrophy and an effusion, although adult patients may present with minimal effusion, called dry or “sicca” arthritis. At this point, plain radiographs demonstrate periarticular osteopenia due to the hyperemic inflammatory response (Fig. 33.3). Granulation tissue develops at the joint periphery leading to marginal erosions. As the disease progresses, this tissue extends across the joint surface directly damaging the articular cartilage (Fig. 33.4a, b). Other osseous abnormalities include osteophytes, chondrocalcinosis, and loose bodies. Ultimately, destruction of the joint occurs with or without subluxation or dislocation (Fig. 33.5a–c). Joints may also become ankylosed, often in a nonfunctional position.

The time course and evolution of pathologic changes are similar to that of an untreated chronic inflammatory arthropathy. Less common entities such as pigmented villonodular synovitis may also be confused with tuberculous arthritis, requiring a biopsy.

The clinical consequences are most profound in the larger, weight-bearing joints, especially the hip. Shanmugasundaram has classified the spectrum of morphologic abnormalities associated with mycobacterial hip disease into seven categories [5] (Fig. 33.6).

Other than biopsy, surgical intervention addresses complications of the disease, and procedures include synovectomy with or without joint debridement, osteotomy, arthrodesis, excisional arthroplasty, pelvic support osteotomy, and total joint arthroplasty.

During the early stages of TB arthritis, when changes are potentially reversible, treatment focuses on controlling discomfort with rest and restoring and maintaining ROM and strength. Adjunctive measures such as physical therapy, traction, serial casting, and/or splinting may help achieve or maintain motion, prevent deformity, provide comfort, and enhance strength. Weight-bearing is encouraged when comfort and an adequate ROM allow. The prognosis is excellent in the early stages, and the indications for synovectomy, with or without joint debridement, remain controversial.

Irreversible changes in the joint occur in the later stages, and salvage procedures can improve function. In cases where ankylosis is expected, the goal for some joints (wrist, knee, foot, and ankle) is to maintain a functional position by splinting or casting. When ankylosis would result in a decrease in function, for example, in the elbow, an excisional arthroplasty can be considered (see Chap. 41). When a joint becomes ankylosed in a nonfunctional position, osteotomy can realign the limb.

With hip involvement, the context will determine whether the goal is stability or motion. Hip arthrodesis can reliably reduce pain and restore alignment but produces increased stresses at the knee and lumbar spine that can lead to degenerative changes over the long term (Fig. 33.7a–d). Excisional arthroplasty will improve motion at the expense of stability, and the resulting gait disturbance can be significant. When the hip has autofused in a nonfunctional position and arthrodesis is an acceptable solution, an osteotomy can reposition the limb (Fig. 33.8a–d). Pelvic support osteotomy should be considered when retention of motion is desirable. When the resources are available, total joint arthroplasty is an option, along with prophylactic chemotherapy to reduce the risks of disease reactivation.